Securing WebLogic Server

Configuring Single Sign-On with Web Browsers and HTTP Clients

The Security Assertion Markup Language (SAML) enables cross-platform authentication between Web applications or Web Services running in a WebLogic Server domain and Web browsers or other HTTP clients. WebLogic Server supports single sign-on (SSO) based on SAML. When users are authenticated at one site that participates in a single sign-on (SSO) configuration, they are automatically authenticated at other sites in the SSO configuration and do not need to log in separately.

The following sections describe how to set up single sign-on (SSO) with Web browsers or other HTTP clients by using authentication based on the Security Assertion Markup Language (SAML) versions 1.1 and 2.0.

Configure the SAML Credential Mapping provider as a SAML authority, using the Issuer URI, Name Qualifier, and other attributes.

Configure the Source Site Federation Services

Configuration of a WebLogic Server instance as a SAML 1.1 source site is controlled by the FederationServicesMBean. Access the FederationServicesMBean with the WebLogic Scripting Tool or through the Administration Console, on the Environment Servers ServerName Configuration Federation Services SAML 1.1 Source Site page. See Configure SAML source services in the Administration Console Online Help.

Configure SAML source site attributes as follows:

Enable the SAML Source Site. Allow the WebLogic server instance to serve as a SAML source site by setting Source Site Enabled to true.

Set Source Site URL and Service URIs. Set the URL for the SAML source site. This is the URL that hosts the Intersite Transfer Service and Assertion Retrieval Service. The source site URL is encoded as a source ID in hex and Base64. When you configure a SAML Asserting Party for Browser/Artifact profile, you specify the encoded source ID.

Also specify the URIs for the Intersite Transfer Service and (to support Browser/Artifact profile) the Assertion Retrieval Service. These URIs are also specified in the configuration of an Asserting Party.

Add signing certificate. The SAML source site requires a trusted certificate with which to sign assertions. Add this certificate to the keystore and enter the credentials (alias and passphrase) to be used to access the certificate. The server’s SSL identity key/certificates will be used by default if a signing alias and passphrase are not supplied.

Configure SSL for the Assertion Retrieval Service. You can require all access to the Assertion Retrieval Service to use SSL by setting FederationServicesMBean.arsRequiresSSL to true. You can require two-way SSL authentication for the Assertion Retrieval Service by setting both arsRequiresSSL and ARSRequiresTwoWaySSL to true.

Configure Relying Parties

A SAML Relying Party is an entity that relies on the information in a SAML assertion produced by the SAML source site. You can configure how WebLogic Server produces SAML assertions separately for each Relying Party or use the defaults established by the Federation Services source site configuration for producing assertion.

You configure a Relying Party in the Administration Console, on the Security Realms RealmName Providers Credential Mapper SAMLCredentialMapperNameManagement Relying Parties page. See Create a SAML Relying Party and Configure a SAML Relying Party in the Administration Console Online Help.

Configure Supported Profiles

When you configure a SAML Relying Party, you can specify support for Artifact profile or POST profile, for the purposes of SAML SSO. As an alternative configure a Relying Party to support WSS/Holder-of-Key or WSS/Sender-Vouches profiles for Web Services Security purposes. Be sure to configure support for the profiles that the SAML destination sites support.

If you support the POST profile, optionally create a form to use in POST profile assertions for the Relying Party and set the pathname of that form in the POST Form attribute.

Assertion Consumer Parameters

For each SAML Relying Party, you can configure one or more optional query parameters (such as a partner ID) that will be added to the ACS URL when redirecting to the destination site. In the case of POST profile, these parameters will be included as form variables when using the default POST form. If a custom POST form is in use, the parameters will be made available as a Map of names and values, but the form may or may not constructed to include the parameters in the POSTed data.

Replacing the Default Assertion Store

WebLogic Server uses a simple assertion store to maintain persistence for produced assertions. You can replace this assertion store with a custom assertion store class that implements weblogic.security.providers.saml.AssertionStoreV2. Configure WebLogic Server to use your custom assertion store class, rather than the default class, using the FederationServicesMBean.AssertionStoreClassName attribute. You can configure properties to be passed to the initStore() method of your custom assertion store class by using the FederationServicesMBean.AssertionStoreProperties attribute. Configure these attributes in the Administration Console on the Environment: Servers ServerNameConfiguration Federation Services SAML 1.1 Source Site page.

Configuring a SAML 1.1 Destination Site for Single Sign-On

The following topics describe how to configure WebLogic Server as a SAML destination site:

Configure Destination Site Federation Services

Before you configure WebLogic as a SAML destination site, you must first create a SAML Identity Assertion Provider V2 instance in your security realm. Configuration of a WebLogic Server instance as a SAML destination site is controlled by the FederationServicesMBean. You can access the FederationServicesMBean using the WebLogic Scripting Tool or through the Administration Console, using the Environment: Servers ServerName Configuration Federation Services SAML 1.1 Destination Site page.

Configure the SAML destination site attributes as follows.

Enable the SAML Destination Site

Allow the WebLogic Server instance to serve as a SAML destination site by setting Destination Site Enabled to true.

Set Assertion Consumer URIs

Set the URIs for the SAML Assertion Consumer Service. This is the URL that receives assertions from source sites, so that the destination site can use the assertions to authenticate users. The Assertion Consumer URI is also specified in the configuration of a Relying Party.

Configure SSL for the Assertion Consumer Service

You can require all access to the Assertion Consumer Service to use SSL by setting FederationServicesMBean.acsRequiresSSL to true.

Add SSL Client Identity Certificate

The SAML destination site uses a trusted certificate with which to sign POST profile responses. Add this certificate to the keystore and enter the credentials (alias and passphrase) to be used to access the certificate.

Configure Single-Use Policy and the Used Assertion Cache or Custom Assertion Cache

Optionally, you can require that each POST profile assertion be used no more than once. WebLogic Server maintains a cache of used assertions so that it can support a single-use policy for assertions. You can replace this assertion cache with a custom assertion cache class that implements weblogic.security.providers.saml.SAMLUsedAssertionCache. Configure WebLogic Server to use your custom assertion cache class, rather than the default class, using the FederationServicesMBean.SAMLUsedAssertionCache attribute. You can configure properties to be passed to the initCache() method of your custom assertion cache class using the FederationServicesMBean.UsedAssertionCacheProperties attribute. You can configure these attributes in the Administration Console on the Environment Servers ServerName Configuration Federation Services SAML 1.1 Destination Site page.

Configure Recipient Check for POST Profile

Optionally, you can require that the recipient of the SAML Response must match the URL in the HTTP Request. Do this by setting the POST Recipient Check Enabled attribute.

Configuring Asserting Parties

A SAML Asserting Party is a trusted SAML Authority (an entity that can authoritatively assert security information in the form of SAML Assertions).Configure an Asserting Party in the Administration Console, using the Security Realms RealmName Providers Credential Mapper SAMLCredentialMapperNameManagement: Asserting Parties page. See Create a SAML Asserting Party and Configure a SAML Asserting Party in the Administration Console Online Help.

Configure Supported Profiles

When you configure a SAML Asserting Party, you can specify support for Artifact profile or POST profile, for the purposes of SAML SSO. Alternatively, configure an Asserting Party to support WSS/Holder-of-Key or WSS/Sender-Vouches profiles for Web Services Security purposes.

Configure Source Site ITS Parameters

For each SAML Asserting Party, configure zero or more optional query parameters (such as a partner ID) that will be added to the ITS URL when redirecting to the source site.

Configuring Relying and Asserting Parties with WLST

SAML partners (Relying Parties and Asserting Parties) are maintained in a registry. You can configure SAML partners using the WebLogic Administration Console or using WebLogic Scripting Tool. The following example shows how you might configure two Relying Parties using WLST in online mode.

Configuring SAML 2.0 Services: Main Steps

A summary of the main steps you take to configure SAML 2.0 services are as follows:

Determine whether you plan to have SAML 2.0 services running in more than one WebLogic Server instance in the domain. If so, do the following:

Create a domain in which the RDBMS security store is configured.

The RDBMS security store is required by the SAML 2.0 security providers so that the data they manage can be synchronized across all the WebLogic Server instances that share that data.

Note that Oracle does not recommend upgrading an existing domain in place to use the RDBMS security store. If you want to use the RDBMS security store, you should configure the RDBMS security store at the time of domain creation. If you have an existing domain with which you want to use the RDBMS security store, create the new domain and migrate your existing security realm to it.

Ensure that all SAML 2.0 services are configured identically in each WebLogic Server instance. If you are configuring SAML 2.0 services in a cluster, each Managed Server in that cluster must be configured individually.

The sections that follow provide details about each set of main steps.

Configuring SAML 2.0 General Services

Regardless of the SAML 2.0 role in which you wish to configure a WebLogic Server instance — that is, as either a Service Provider or Identity Provider — you need to configure the server’s general SAML 2.0 services. Configuration of the SAML 2.0 general services for a WebLogic Server instance is controlled by the SingleSignOnServicesMBean. You can access the SingleSignOnServicesMBean with the WebLogic Scripting Tool or through the Administration Console, on the Environment Servers ServerName Configuration Federation Services SAML 2.0 General page.

Note:

You cannot configure SAML 2.0 general services in a WebLogic Server instance until you have first configured either the SAML 2.0 Identity Assertion or SAML 2.0 Credential Mapping provider and restarted the server instance.

About SAML 2.0 General Services

The general SAML 2.0 services you configure include the following:

Whether you wish to enable the replicated cache

Enabling the replicated cache is required if you are configuring SAML 2.0 services on two or more WebLogic Server instances in a domain, such as in a cluster. The replicated cache enables server instances to share and be synchronized with the data that is managed by the SAML 2.0 security providers; that is, either or both the SAML 2.0 Identity Assertion provider and the SAML 2.0 Credential Mapping provider.

Note that the RDBMS security store is strongly recommended if you enable the replicated cache. Therefore prior to configuring SAML 2.0 services, the preferred approach is first to create a domain that is configured to use the RDBMS security store. For more information, see Managing the RDBMS Security Store.

Information about the local site

The site information you enter is primarily for the benefit of the business partners in the SAML federation with whom you share it. Site information includes details about the local contact person who is your partners’ point of contact, your organization name, and your organization’s URL.

Published site URL

This URL specifies the base URL that is used to construct endpoint URLs for the various SAML 2.0 services. The published site URL should specify the host name and port at which the server is visible externally, which might not be the same at which the server is accessed locally. For example, if SAML 2.0 services are configured in a cluster, the host name and port may correspond to the load balancer or proxy server that distributes client requests to the Managed Servers in that cluster.

The published site URL should be appended with /saml2. For example:

https://www.avitek.com:7001/avitek-domain/aviserver/saml2

Entity ID

The entity ID is a human-readable string that uniquely distinguishes your site from the other partner sites in your federation. When your partners need to generate or consume an assertion, the SAML 2.0 services use the entity ID as part of the process of identifying the partner that corresponds with that assertion.

Whether recipient check is enabled

If enabled, the recipient of the authentication request or response must match the URL in the HTTP Request.

Whether TLS/SSL client authentication is required for invocations on the Artifact Resolution Service. If enabled, SAML artifacts are encrypted when transmitted to partners.

Transport Layer Security keystore alias and passphrase, used for retrieving the server’s keys that are used for securing outgoing communications with partners.

Whether Basic authentication client authentication is required when your partners invoke the HTTPS bindings of the local site.

If you enable this setting, you also specify the client username and password to be used. These credentials are then included in the published metadata file that you share with your federated partners.

Whether requests for SAML artifacts received from your partners must be signed.

Configuration settings for the SAML artifact cache.

Keystore alias and passphrase for the key to be used when signing documents sent to your federated partners, such as authentication requests or responses.

Publishing and Distributing the Metadata File

The local site information that is needed by your federated partners — such as the local site contact information, entity ID, published site URL, whether TLS/SSL client authentication is required, and so on — is published to a metadata file by clicking Publish Meta Data in the SAML 2.0 General console page.

When you publish the metadata file, you specify an existing directory on the local machine in which the file can be created. The process of distributing the metadata file to your federated partners is a detail that is not implemented by WebLogic Server. However, you may send this file via a number of commonly used mechanisms suitable for securely transferring electronic documents, such as encrypted email or secure FTP.

Keep the following in mind regarding the metadata file:

Before you publish the metadata file, you should configure the Identity Provider and/or Service Provider services for the SAML 2.0 roles in which the WebLogic Server instances in your domain are enabled to function.

The configuration data for the SAML 2.0 services your site offers that is needed by your federated partners is included in this metadata file, greatly simplifying the tasks your partners perform to import your signing certificates, identify your site’s SAML 2.0 service endpoints, and use the correct binding types for connecting to your site’s services, and so on.

You should have only a single version of the metadata file that you share with your federated partners, even if your site functions in the role of Service Provider with some partners and Identity Provider with others. By having only a single version of the metadata file, you reduce the likelihood that your configuration settings might become incompatible with those of a partner.

If you change the local site’s SAML 2.0 configuration, you should update your metadata file. Because the metadata file is shared with your partners, it will be convenient to minimize the frequency with which you update your SAML 2.0 configuration so that your partners can minimize the need to make concomitant updates to their own partner registries.

When you receive a metadata file from a federated partner, place it in a location that can be accessed by all the nodes in your domain in which SAML 2.0 services are configured. At the time you create a partner, you bring the contents the partner’s metadata file into the partner registry.

Configure SAML 2.0 Identity Provider Services

Configuration of a WebLogic Server instance as a SAML 2.0 Identity Provider site is controlled by the SingleSignOnServicesMBean. You can access the SingleSignOnServicesMBean using the WebLogic Scripting Tool (WLST), or through the Administration Console by using the Environment Servers ServerName Configuration Federation Services SAML 2.0 Identity Provider page.

Enable the SAML 2.0 Identity Provider Site

From the SAML 2.0 Identity Provider page in the console, allow the WebLogic Server instance to serve as an Identity Provider site by setting the Enabled attribute to true.

Specify a Custom Login Web Application

Optionally, you may use a custom login web application to authenticate users into the Identity Provider site. To configure a custom login web application, enable the Login Customized attribute and specify the URL of the web application.

Enable Binding Types

Oracle recommends enabling all the available binding types for the endpoints of the Identity Provider services; namely, POST, Redirect, and Artifact. Optionally you may select a preferred binding type.

Publish Your Site’s Metadata File

After you have configured the SAML 2.0 general services and Identity Provider services, publish your site’s metadata file and distribute it to your federated partners, as described in Publishing and Distributing the Metadata File.

Create and Configure Web Single Sign-On Service Provider Partners

A SAML 2.0 Service Provider partner is an entity that consumes the SAML 2.0 assertions generated by the Identity Provider site. The configuration of Service Provider partners is available from the Administration Console, using the Security Realms RealmName Providers Credential Mapper SAML2CredentialMapperNameManagement page.

The attributes that can be set on this console page can also be accessed programmatically via a set of Java interfaces, which are identified in the sections that follow.

Obtain Your Service Provider Partner’s Metadata File

Before you configure a Service Provider partner for web single sign-on, you need to obtain the partner’s SAML 2.0 metadata file via a trusted and secure mechanism, such as encrypted email or an SSL-enabled FTP site. Your partner’s metadata file describes the partner site and binding support, includes the partner’s certificates and keys, contains your partner’s SAML 2.0 service endpoints, and more. Copy the partner’s metadata file into a location that can be accessed by each node in your domain configured for SAML 2.0.

Configure How Assertions are Generated

Optionally from the General tab of the partner configuration page in the console, you can configure the following attributes of the SAML 2.0 assertions generated specifically for this Service Provider partner:

The Service Provider Name Mapper Class name

This is the Java class that overrides the default username mapper class with which the SAML 2.0 Credential Mapping provider is configured in this security realm.

Time to Live attributes

The Time to Live attributes specify the interval of time during which the assertions generated for this partner are valid. These attributes prevent expired assertions from being used.

Whether to generate attribute information that is included in assertions

If enabled, the SAML 2.0 Credential Mapping provider adds, as attributes in the assertion, the groups to which the corresponding user belongs.

Whether the assertions sent to this partner must be disposed of immediately after use

Whether this server’s signing certificate is included in assertions generated for this partner

The attributes for specifying whether this partner accepts only signed assertions, or whether authentication requests must be signed, are read-only: they are derived from the partner’s metadata file.

Configure Artifact Binding and Transport Settings

Optionally, you also use the General tab of the Service Provider partner configuration page to configure the following:

Whether SAML artifacts are delivered to this partner via the HTTP POST binding. If so, you may also specify the URI of a custom web application that generates the HTTP POST form for sending the SAML artifact.

The URI of a custom web application that generate the HTTP POST form for sending request or response messages via the POST binding.

For added security in the exchange of documents with this partner, you can also specify a client user name and password to be used by the Service Provider partner when connecting to the local site’s binding using Basic authentication. This attribute is available via the com.bea.security.saml2.providers.registry.BindingClientPartner Java interface.

Configure the SAML 2.0 Identity Assertion Provider

In your security realm, create an instance of the SAML 2.0 Identity Assertion provider. The SAML 2.0 Identity Assertion provider is not part of the default security realm. The attributes you specify for the SAML 2.0 Identity Assertion provider include the following:

Whether the replicated cache is enabled

If you are configuring SAML 2.0 Identity Provider services in two or more server instances in the domain, this attribute must be enabled.

A custom name mapper class that overrides the default SAML 2.0 assertion name mapper class

Configure the SAML Authentication Provider

If you plan to enable virtual users, or consume attribute statements contained in assertions that you receive from your Identity Provider partners, you need to create and configure an instance of the SAML Authentication provider. For more information, see Configuring the SAML Authentication Provider.

Configure SAML 2.0 General Services

After configuring the SAML 2.0 Identity Assertion provider, and optionally the SAML Authentication provider, configure the SAML 2.0 general services, as described in Configuring SAML 2.0 General Services.

Configure SAML 2.0 Service Provider Services

Configuration of a WebLogic Server instance as a SAML 2.0 Service Provider site is controlled by the SingleSignOnServicesMBean. You can access the SingleSignOnServicesMBean using the WebLogic Scripting Tool (WLST), or through the Administration Console using the Environment Servers ServerName Configuration Federation Services SAML 2.0 Service Provider page.

You configure the SAML 2.0 Service Provider site attributes as summarized in the sections that follow. For more information about these configuration tasks, see Configure SAML 2.0 Service Provider services in the Administration Console Online Help.

Enable the SAML 2.0 Service Provider Site

From the Federation Services: SAML 2.0 Identity Provider page in the console, allow the WebLogic Server instance to serve as a Service Provider site by setting the Enabled attribute to true.

Specify How Documents Must Be Signed

Optionally you may enable the attributes that set the following document signing requirements:

Whether authentication requests sent to Identity Provider partners are signed

Whether assertions received from Identity Provider partners are signed

Specify How Authentication Requests Are Managed

Optionally you may enable the following attributes of the authentication request cache:

Maximum cache size

Time-out value for authentication requests, which establishes the time interval beyond which stored authentication requests are expired

Enable Binding Types

Oracle recommends enabling all the available binding types for the endpoints of the Service Provider services; namely, POST, Redirect, and Artifact. Optionally you may specify a preferred binding type.

Set Default URL

Optionally, you may specify the URL to which unsolicited authentication responses are sent if they do not contain an accompanying target URL.

Create and Configure Web Single Sign-On Identity Provider Partners

A SAML 2.0 Identity Provider partner is an entity that generates SAML 2.0 assertions consumed by the Service Provider site. The configuration of Identity Provider partners is available from the Administration Console, using the Security Realms RealmName Providers Authentication SAML2IdentityAsserterNameManagement page.

The attributes that can be set on this console page can also be accessed programmatically via a set of Java interfaces, which are identified in the sections that follow.

The following sections summarize tasks for configuring an Identity Provider partner.

Obtain Your Identity Provider Partner’s Metadata File

Before you configure an Identity Provider partner for web single sign-on, you need to obtain the partner’s SAML 2.0 metadata file via a trusted and secure mechanism, such as encrypted email or an SSL-enabled FTP site. Your partner’s metadata file describes that partner site and binding support, includes the partner’s certificates and keys, and so on. Copy the partner’s metadata file into a location that can be accessed by each node in your domain configured for SAML 2.0.

Configure Authentication Requests and Assertions

Optionally, you can configure the following attributes of the authentication requests generated for, and assertions received from, this Identity Provider partner:

The Identity Provider Name Mapper Class name

This is the custom Java class that overrides the default username mapper class with which the SAML 2.0 Identity Assertion provider is configured in this security realm. The custom class you specify is used only for identities contained in assertions received from this particular partner.

Whether to consume attribute information contained in assertions received from this partner

If enabled, the SAML 2.0 Identity Assertion provider extracts attribute information from the assertion, which it uses in conjunction with the SAML Authentication provider (which must be configured in the security realm) to determine the groups in the security realm to which the corresponding user belongs.

Configure Binding and Transport Settings

Optionally, you also use the General tab of the Service Provider partner configuration page to configure the following:

Whether SAML artifacts are delivered to this partner via the HTTP POST method. If so, you may also specify the URI of a custom web application that generates the HTTP POST form for sending the SAML artifact.

The URL of the custom web application that generates the POST form for carrying the SAML response for POST bindings to this Identity Provider partner.

The URL of the custom web application that generates the POST form for carrying the SAML response for Artifact bindings to this Identity Provider partner.

For added security in the exchange of documents with this partner, you can also specify a client user name and password to be used by this Identity Provider partner when connecting to the local site’s binding using Basic authentication. This attribute is available via the com.bea.security.saml2.providers.registry.BindingClientPartner Java interface.

Viewing Partner Site, Certificate, and Service Endpoint Information

When you configure SAML 2.0 partners, the partner configuration pages displayed by the Administration Console include tabs for viewing and configuring the following additional information about the partner:

The Site tab displays information about the Service Provider partner, which is derived from the partner’s metadata file. The data in this tab is read-only.

When configuring Identity Provider partners, the Single Sign-On Service Endpoints tab is available, which displays the Identity Provider partner’s single sign-on service endpoints. This data is also available from the com.bea.security.saml2.providers.registry.WebSSOIdPPartner Java interface.

Deployment Descriptor Recommendations

Note the following recommendations regarding the use of the following elements in deployment descriptor files:

relogin-enabled

cookie-name

Use of relogin-enabled with CLIENT-CERT Authentication

If a user logs in to a web application and tries to access a resource for which that user is not authorized, an HTTP FORBIDDEN (403) response is generated. This is standard web application behavior. However, for backwards compatibility with earlier releases, WebLogic Server permits web applications to use the relogin-enabled element in the weblogic.xml deployment descriptor file, so that the response to an access failure results in a request to authenticate. In certain circumstances, it can cause SAML 2.0 based web single sign-on to fail.

Normally, the SAML 2.0 Assertion Consumer Service (ACS) logs the user into the application and redirects the user request to the target web application. However, if that web application is enabled for SAML 2.0 single sign-on, is protected by CLIENT-CERT authentication, and has the relogin-enabled deployment descriptor element set to true, an infinite loop can occur in which a request to authenticate a user is issued repeatedly. This loop can occur when a user is logged in to the web application and attempts to access a resource for which the user is not permitted: instead of generating a FORBIDDEN message, a new authentication request is generated that triggers another SAML 2.0 based web single sign-on attempt.

To prevent this situation from occurring in a web application that is protected by CLIENT-CERT authentication, either remove the relogin-enabled deployment descriptor element for the web application, or set the element to false. This enables standard web application authentication behavior.

Use of Non-default Cookie Name

When the Assertion Consumer Service logs in the Subject contained in an assertion, an HTTP servlet session is created using the default cookie name JSESSIONID. After successfully processing the assertion, the ACS redirects the user’s request to the target web application. If the target web application uses a cookie name other than JSESSIONID, the Subject’s identity is not propagated to the target web application. As a result, the servlet container treats the user as if unauthenticated, and consequently issues an authentication request.

To avoid this situation, do not change the default cookie name when deploying web applications in a domain that are intended to be accessed by SAML 2.0 based single sign-on.

Login Application Considerations for Clustered Environments

Note the following two login limitations that are rare in clustered environments, but if they occur, they may prevent a single sign-on session from succeeding.

When an Identity Provider’s single sign-on service receives an authentication request, it redirects that request to the login application to authenticate the user. The login application must execute on the same cluster node as that single sign-on service. If not, the Identity Provider is unable to produce a SAML 2.0 assertion even if the authentication succeeds.

Under normal circumstances, the login application executes on the same node as the single sign-on service, so likelihood of the authentication request being redirected to a login application executing on a different node in the domain is very small. However, it may happen if an authentication request is redirected by a cluster node different than the one hosting the login application. You can almost always prevent this situation from occurring if you configure the Identity Provider to use the default login URI with Basic authentication.

When the SAML 2.0 Assertion Consumer Service (ACS) successfully consumes an assertion, it logs in the Subject represented by the assertion. The ACS then redirects the user request to the target application. Normally, the target application executes on the same node as the ACS. However, in rare circumstances, the target application to which is the user request is redirected executes on a cluster node other than the one hosting the ACS on which the login occurred. When this circumstance occurs, the identity represented by the assertion is not propagated to the target application node. The result is either another attempt at the single sign-on process, or denied access.

Because the target application executes on the same node as the ACS, this situation is expected to occur very rarely.